Docker: Accelerated Container Application Development

 

Docker: Accelerated Container Application Development

1. Developers can deploy, run, and manage applications.

2. Deploy applications quickly.

3. Docker is a containerization platform that simplifies the process of deploying and managing applications. Applications run along with their dependencies. 

Docker Images :

1. A copy of our project.

2. Images are made from source code, libraries, and external dependencies.

3. Images are created from source code.

4. Example: Node setup, application code, installed libraries, Docker files.

5. Once an image is created, it cannot be updated; we can create a new image instead.

Docker Container :

1. A container runs applications using images.

2. Containers run independently.

3. Example: If 3 images are available, all these images can run independently.  

Docker Commands :

1. docker build -t folder/dockername . // Creates a project image.

2. docker run -p 5000:5000 -d dockerImageName // Runs a container.

3. docker ps // Shows all running containers.

4. docker logs container_id // Displays project logs.

5. docker image prune // Removes unused images.

6. docker service scale web-app=2 // Scales the web-app service to two replicas.

7. docker service update --image <new-image> service_name // Updates a Docker container's image without causing downtime. 

Docker File Example :

1. Create a file named Dockerfile in the root directory of your backend project.

2. In this Dockerfile, write the following code:

# Use Node.js version 20 as the base image

FROM node:20  

# Set the working directory inside the container

WORKDIR /node-practical  

# Copy package.json and package-lock.json to the working directory

COPY package*.json ./  

# Install dependencies

RUN npm install  

# Copy the entire project to the container

COPY . .  

# Specify the command to run the application

CMD ["node", "index.js"]

3. Here’s an example of a docker-compose.yml file for a microservices architecture:

    docker-compose.yml Example : 

version: '3.9'

services:

  db:

    image: postgres:14-alpine

    restart: always

    environment:

      POSTGRES_USER: postgres

      POSTGRES_PASSWORD: DBPass@123

      POSTGRES_DB: DBNAME

      POSTGRES_HOST_AUTH_METHOD: trust        

     

  gateway:

    build:

      dockerfile: Dockerfile

      context: ./gateway

    command: npm run start:prod

    restart: always  

    ports:

      - "5000:5000"

    depends_on:

      - db      

    environment:

      JWT_SECRET: secret@123

      JWT_EXPIRESIN: 2d

      REDIS_HOST: localhost

      REDIS_PORT: 6379

      REDIS_DB: TestFinAssetMgmt //if use redis

    volumes:          

      - /gateway/src/app/node_modules

 

  auth:

    build:

      dockerfile: Dockerfile

      context: ./auth

    command: npm run start:prod

    restart: always

    ports:

      - "5100:5100"

    depends_on:

      - db      

    environment:

      DB_TYPE : postgres

      DB_HOST : HOST_name

      DB_PORT : 5432

      DB_USERNAME : DBUSERNAME

      DB_PASSWORD : DB PASS

      DB_DATABASE : DBDATABASENAME

      DB_SYNC : true

      JWT_SECRET : secret@123

      JWT_EXPIRESIN : 2d

      RESET_PASSWORD_URL : http://3.15.153.226:3000

    volumes:          

      - /auth/src/app/node_modules

  mail:

    build:

      context: ./mail

    command: npm run start:prod

    restart: always

    ports:

      - "5200:5200"

    depends_on:

      - db

      - auth

      - gateway      

    environment:

      EMAIL_HOST : smtp.gmail.com

      EMAIL_USER : SMTP-email-pass

      EMAIL_PASSWORD : smtp-password

    volumes:          

      - /mail/src/app/node_modules